Brain disorders, such as substance abuse (drugs and alcohol) and psychiatric problems, are highly prevalent among impoverished Kenyans, and the abundance of locally produced substances (alcohol, cannabis, and khat), absence of evidence-based treatment for substance abuse or psychiatric problems, and associations between these brain disorders and HIV/AIDS, makes this a major public health concern in need of innovative solutions. Untreated substance abuse is associated with decreased reasoning and judgment, playing an important role in sexual transmission and acquisition of HIV/AIDS, and is also linked with low medication adherence, disease susceptibility, and progression to AIDS. Our research team has found motivational interviewing (MI), an evidence-based substance abuse treatment traditionally delivered in-person, to be effective at decreasing alcohol abuse in the Kenyan cultural context. The objective of this R21 application is to develop a mobile phone-based (mobile MI) intervention for substance abuse provided by MI-trained Kenyan clinicians, as an innovative approach to lowering the cost, decreasing time to treatment, and reducing the treatment gap for impoverished Kenyans who rarely interact with highly trained clinicians. In response to PA- 11-031, Brain Disorders in the Developing World, we propose the following aims: 1) Assess feasibility, acceptability, and efficacy of using mobile phones to provide MI to substance abusing adults, and 2) Quantify the varying response to MI treatment for participants with psychiatric problems and identify areas for future intervention.